
https://leetcode.com/problems/max-number-of-k-sum-pairs/
class Solution:
def maxOperations(self, nums: List[int], k: int) -> int:
if len(nums) == 1:
return 0
nums = sorted(nums)
l, r = 0, len(nums) - 1
res = 0
while l < r:
if nums[l] + nums[r] == k:
res += 1
l += 1
r -= 1
elif nums[l] + nums[r] > k:
r -= 1
elif nums[l] + nums[r] < k:
l += 1
return res